Title

Authors

Date of this Version

Fall 12-2010

Comments

A THESIS
Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For Degree of Master of Science,
Major: Food Science & Technology,
Under the Supervision of Professor Michael G. Zeece.
Lincoln, Nebraska:
December 2010
Copyright 2010 Andrew Hoppe.

Abstract

Egg white proteins have become an important and desirable ingredient to the food industry due to their functional properties which include gelling, foaming, and emulsification. Egg white is also well recognized as an excellent source of nutrition. The goal of this work was to determine the effects of high pressure (HP) treatment on egg white proteins. Specifically, experiments were conducted using Raman spectroscopy and pepsin digestibility to investigate structural changes. Pressure treatment at 400 to 800 MPa (5 minutes at 4°C) resulted in increased pepsin digestibility of egg white proteins ovalbumin, ovotransferrin, and lysozyme compared to heat-treated (85 to 95°C) and untreated controls. Increased digestibility was also evident at pressures that did not result in gelation. Raman spectroscopy analysis of protein secondary structural changes resulting from HP-treatment showed an increase in β-sheet/α-helix ratio at these pressure ranges. ACE inhibitor peptide YAEERYPIL (origin ovalbumin) was identified from 800 MPa pepsin digestion sample via Liquid Chromatography/mass spectrometry/mass spectrometry (LC/MS/MS). HP-induced changes in egg white functionality were evaluated by determining foaming and gelation properties with and without prior pressure treatment. Gels were formed at pressures of 600 to 800 MPa and with heat treatment of 85°C to 95°C. HP gels were softer and more elastic than heat treated gels. Lowering the pH to 6 with tartaric acid improved overall gel appearance. With respect to foaming properties, HP increased foam capacity while decreasing stability. Overall, HPP improved egg white functional properties and has the potential to improve egg white nutritional value through increased digestibility.